计算：x+y分之2+x的平方-y的平方分之4y

题目

计算：x+y分之2+x的平方-y的平方分之4y

答案

原式=2(x-y)/(x+y)(x-y)+4y/(x+y)(x-y)
=(2x-2y+4y)/(x+y)(x-y)
=2(x+y)/(x+y)(x-y)
=2/(x-y)